Goals from Momo Sissoko and Pavel Nedved gave Juve the lead at half-time following Davide Biondini’s opener, but Brazilian Jeda and Alessandro Matri struck after the break to record a famous victory for the Sardinians.

It means second-placed Juventus, who lost their second game in a row, could fall to nine points behind leaders Inter Milan if the champions win at home to Torino on Sunday.

Juve coach Claudio Ranieri was magnanimous in defeat but admitted he didn’t know what was wrong with his team.

“They deserved it. They played great, they were organised and that’s not a surprise when you saw how they played against Inter and Lazio,” he said.

“In the last two games we’ve conceded five goals so naturally there’s something that’s not right. We were hoping to create goalscoring chances but we didn’t.”

For Cagliari it was a fourth straight victory and leaves them unbeaten in five matches — their only dropped points where in a 1-1 draw at Inter — since the turn of the year.

It also means that since the first five games of the season — all of which they lost — only Inter have won more points than Cagliari, who are now challenging for a Champions League qualification finish.

But Cagliari coach Massimiliano Allegri said his team couldn’t rest on their laurels.

“We have a great capacity to work hard but if we lose this desire to work, regardless of our technical qualities, we will become a normal team again, or worse still, the one we were at the beginning of the season,” he said.

Juventus came close to breaking the deadlock on 12 minutes as the excellent Sissoko played a one-two with Amauri before poking wide as he stretched for the return.

Cagliari sprung a surprise on 16 minutes, though, as they took the lead following some shoddy defending by the hosts.

Michele Fini sent over a deep cross from the right to the back post where the dimunitive Marco Marchionni was left to mark Biondini who easily climbed above his man to head powerfully past Gianluigi Buffon.

The lead lasted only a quarter of an hour before Sissoko levelled matters, rising highest in the box to head home an Alessandro Del Piero corner.

Things got even better for Juve on 38 minutes as Nedved’s cross into the box was only half cleared and the Czech veteran himself followed up to smash home a half-volley from just inside the area.

Juventus were looking good at the break but Cagliari turned the match on its head after the restart with two clinical counter-attacks.

On 54 minutes, Andrea Cossu ran down the left flank and crossed into the centre where Jeda beat the onrushing Buffon.

Del Piero came within inches of giving Juventus the lead from a free-kick but on 78 minutes two Cagliari substitutes combined to stun the home crowd.

Matri played a one-two with Andrea Lazzari before finding himself in the clear and he comfortably slotted past Buffon. Earlier, Napoli gave up a two-goal lead in a 2-2 draw with Udinese in Naples.

Argentina forward Ezequiel Lavezzi gave the hosts the lead on 24 minutes with a deflected shot that wrong-footed Slovenian goalkeeper Samir Handanovic.

Just three minutes later highly-rated Slovakia midfielder Marek Hamsik headed home a Walter Gargano free-kick.

But Udinese were level by half-time, thanks in no small part to a controversial penalty decision when Christian Zapata threw himself to the ground despite no contact from Paolo Cannavaro.

Antonio Di Natale scored from the spotkick before Fabio Quagliarella scored a stunning leveller on the stroke of half-time with a first-time volley from